What dosage of zinc should be taken to prevent colds?

Smaller doses: Zinc in lower daily doses say 12.5 to 25 mg can help prevent colds by keeping immune functions balanced. But, too much zinc can be toxic long term. In an acute situation with a cold that has started 25 mg in lozenge form slowly dissolved in the mouth can shorten a colds duration and severity. The lozenge route is only one that works well as this is a local mucosal event, pills don't work well.